University of Pittsburgh, Pittsburgh, PA, USA, 3 Department of this website Otorhinolaryngology, University of Duisburg-Essen, Essen, Germany Human solid tumors have evolved numerous strategies for escape from the host immune system. Recently, it has been shown that regulatory T cells (Treg) accumulate in blood and tissues of patients with cancer influencing prognosis. One mechanism for Treg-mediated suppression of anti-tumor immunity involves ectonucleotidases CD39 and CD73 overexpressed on CD4+CD25highFOXP3+ cells. These enzymes sequentially convert ATP into AMP and adenosine, which binds to A2a receptors (A2aR) on effector cells, suppressing their functions. Treg express low levels of adenosine deaminase

(ADA) responsible for adenosine breakdown and of CD26, a surface-bound glycoprotein associated with ADA. Inhibitors of ectonucleotidases or antagonists of the A2aR block Treg-mediated suppression. The increased frequency and suppressor activity of Treg in patients with cancer are in part regulated by the presence in body fluids of tumor-derived microvesicles (TMV)

also referred to as exosomes. When isolated and purified from tumor cell supernatants or sera of selleck kinase inhibitor patients with cancer, TMV induced conversion Anlotinib solubility dmso of CD4+CD25neg into CD4+CD25highFOXP3+ Treg and enhanced Treg proliferation (p